Automatic power controller for pneumatic-dispatch systems



Feb. 4, 1930. c. 5. JENNINGS AUTOMATIC POWER CONTROLLER FOR PNEUMATIC DISPATCH SYSTEflS Filed Jan. 18. 1926- 2 Shets-Sheet Feb. 4, 1930. c. 5. JENNINGS 7 AUTOMATIC POWER CONTROLLER FOR PNEUMATIC DISPATCH SYSTEMS Filed Jan. 18, 1926 r 2 Sheets-Sheet 2 'T/'- I 4 ,L -J. 07 /Z (If? 1 4; if 0 J3 4 49 9.2 17 ifi ffii iif' J3 44/ 19 6 4f 4 d/ c4 J2 VZ/ /0 l Z; /r I I 5' 22 :3 /7 4 /4 f J9 k 9 a7 a7 46 60 Z0 24 a a2: f 47 a? M *ii'iiiiii-tizf (if I 2 J6 7 1 29 I I P I w 40 2/ air m 14 d /r 6? ya /9 /6 v an 20 gztor. I 6,2665%? c/ nnz'iys aiijys.

' flow vacuum type and relatesfmore particularly to automatic power controlling apparatus for use in such a system. 4 Powerrcontrol apparatusof this general Parent -arch. :4, 1930 UNIT E D'V "STATES.

CHESTER sQJEnNiNGs, or s-rrvaousn, NEW-YORK, AssIG'NoR To TI-in LAMSON coM- PATENT .QFFIFCLE.

PANY, or SYRACUSE, new roam- CORPORATION or MASSACHUSETTS AUTOMATIC POWER CONTROLLER FOR'PNEUMATIC-DISPATCH SYSTEMS Q Application filed January. 18,- 1926. Serial No. 1,974. v

This invention pertains to pneumaticv dis.- patch systems of the so-called minimum character is disclosed in the patent to Libby No, 968,576, dated August30, 1910.] The patented apparatus. provides automaticpres sure actuated means for initlatlng a carrier propelling air flow through the transmission tube whenever a CttlllQIYlS entered thereinas well as means for cutting off such flowafter the lapse of a predetermined period of time.

W'Vhile I regard the patented device as gen erally correct in principle and highly efiective in practice I believeit'preferablej to have the cessation of carrier propelling air flow depend directly upon the. discharge of the carrier from the delivery end of the tube rather than upon the operationiof a timing device, and the principal objectrof this-invention is to provide an improved power controtapparatus comprising means actuable automatically upon' nsertion of a earner within the dispatch terminal to initiate flow of a. pneumatic system having the improved of the air propelling current and also operating automatically whe'nthe: last carrier emerges from the delivery terminal to cut off the air current without appreciable delay. Y Inthe closed one preferred embodiment of. the

vention by way of'example'z Fig. 1 being a fragmentary elevation'illustrating a part of the central station desk power control apparatus applied thereto;

Fig. 2 being a fragmentary vertical section. toilarger scale through the "upper part .gof the suctiontube showing the improved power control device applied 'thereto,.'-and showing theflow controlling valve closed.;.,

Fig. 3 is a view similar to :Fig. 2 but showing the flow controlling valve wide open in the position which itiocjcupies during the flight of the carrier; I I 7 Fig. at is a view similar to Fig.2 showing the main valve just at the instant of closing andthe controlling means occupying the p05 accompanying drawings I have dissition assumed at the discharge of the; cari '7 Fig. 5 is a horizontal section substantially horizontal section substantially,

system comprising transmission tubes, such for example as the tube 2 which leads vfrom] the central station to a remote sending Sta tion and then back to the central station desk.

ltach tube 2 i'sfurnished with a delivery ter- V minal 3 and is provided with a continuation 4 connecting it to an individual power control device indicated generally by the numeral 5...

This power control device is connected in turn by means of a suction tube 7 tea vacuum drum or header 8 in which a low pressureis continually maintainedby means of a suitable pump,' exhauster or'equivalent. apparatus, not shown.

An open ended dispatch terminal 6 is pro-' vided atv the central station for each of the transmission tubes 2, such dispatch terminal forming the entrance to that run of the tube which leads to the corresponding remotesend ing station. The above arrangement in general is old and'well known in this art 'and' "further details of such general arrangement are therefore unnecessary, the presentinven tionbeing confined to improvements in the 7 power control apparatus per se.

Referring particularly to Figs 2 3 and.

4:, the numeral 8 designates :a substantially the casing of the powercontrol device,.thel

cylindrical and. vertically disposed portion of part 8 being provided with a flange 9 at its lower end for the reception of the upper end of the suction tube 7 The casing of the power control device also comprises a laterally extending portion 10 having a flange 1O adapted to receive the lower end of a tube 11- which T formsa portion of the casing of thepower control apparatus. The tube 11 is preferably of a diameter somewhat greater than thatof fined by an annular valve seat 16, fitting snuge ly within the upper end of the suction tube 7, or as shown, being seated between the upper end of the tube 7 and'a shoulder formed upon the inner wall of the flange 9. The central opening in the valve seat 16 is of sufficient area to provide for the full flow of air necessary for propelling a carrier through the transmission tube, and this central aperture in the valve seat is normally closed by the main flow-controlling valve now to be described.

This valve preferably comprises a main portion'17 which may be of metal or other suitable material and which is preferably pro- .vided with a washer 18 of rubber or other resilient material and which normally bears I against the surface of the valve seat 16. The

main member 17 of the valve'is furnished with one or more apertures 19 disposed -eccentrically with respect to its axis and these apertures are normally closed by the secondary or pilot member of the valve. This pilot member preferably comprises a disc 22 preferably furnished on its under side with a resilient Washer 23 which bears against the upper face of the main member 17 of the valve.

The main member 17 is furnished with an opening at its center and with a guide sleeve 20 surrounding this opening and extending downwardly from its lower face. A valve actuating stem 21 passes freely through the central opening in the main member 17 of the valve and through the guide sleeve 20, and the pilot member 22 of the valve is securely fixed to this stem. The stem 21 is furnished with an abutment collar 24 at a point normally spaced from the lower end of the sleeve 20, the arrangement being such that whenthe guide stem is moved upwardly the pilot member 22 first rises and uncovers the apertures 19, and thereafter the abutment 24 engages the sleeve 20 and lifts the main member 17 of the valve from its seat 16.

The upper end of the chamber 15 is closed, preferably by means of a removable cover plate 25 and this plate supports a guide sleeve 26 through which the upperpart of the valve stem 21 passes- A motor casing is mounted upon the plate 25. This motor casing comprises a lower member 27 and an upper member 28, said members being provided with engaging flanges by means of which they are bolted together.

The motor casing provides upper and lower chambers 29 and 30 respectively, separated by a flexible diaphragm 31, the edge of which is clamped between the flanges of the members 27 and 28 of the casing.

While I have herein shown a flexible diaphragm'as constituting the movable element of the motor, I contemplate that other and equivalent motor means, such for example as pistons, bellows and the llke may be substituted therefor, and I may hereafter refer to this movable motive member as a pneumatic, this term being one which is familiar to those skilled.in the art as comprehensive of any of the usual air actuated motive devices.

The upper end of the valve stem 21 is preferably furnished with a radial flange 32 and isscrew-threaded at 33. A weight 34 has threaded engagement with the screwthreaded portion 33 of the stem and this weight constitutes a clamping, nut for securing the central part of the member 31 to the stem 21. The lower chamber 30 of the motor casingcommunicates freely with the external air by means of an opening 35.

An auxiliary valve casing is mounted upon the upper part of the motor casing and this valve casing preferably comprises a substantially horizontal tubular portion 37 and a hollow foot 38 which is attached to the member 28 so that it is concentric with an opening 89in the wall of the member 28, the end portions of the part 37 providing passages of large capacity diverging from the passage in thefoot 38. By the expression passages of largecapacity l desire merely to distinguish from bleeder valves or similar slow leak orifices intended to produce a timing effect, the passages here employed, when opened, permitting a rapid pressure change in the chamber 29.

The opposite ends of the horizontal portion 37 of the auxiliary valve casing are preferably furnished with cover plates 40 and lrespectively, and these cover plates are furnished with one or more large eccentric valve apertures or ports 42 (Fig. 6) and with central guide openings. The central guide openings of the two cover plates are aligned with one another and are adapted to receive and to guide the stem portion 44: of the auX- iliary valve device. This valve device comprises apair of spaced heads, the head 45 being attached to the left hand end of the Samar as shown in Fig. 2 and being provided with a resilient pad 46 adapted to cooperate with the plate ll to close the apertures 12 therein.

The other valve head 47 is likewise furnished taneously opening the ports. in the cover 40.

. ject to pressure conditions 1 .15

" to decreasev its weight.

The shaft52 extends outwardly through the 7 56 for counterbalancing the vane 53.

posed within the chamber- 13. The stem 44 of the auxiliary valve extends beyondthe head 47 and is preferably guided in anopening in a bracket 49 attached to the'cover memberf28 of themotor. A spring O is interposed between the bracket 49, and the valve head 47 andnormally holds the aux iliary valve deviceinthe position shown in Fig. 2 wherein the ports 42 in the head 41 j are open and the ports in; the head are 3 closed; As thus disposed, theupper cham-* I provides-a bearing for a transverse shaft 52 which supports an actuator vane'53. This I vane is preferablyof substantially circular- P contour and is normally disposed transversely across the chamber 13 immediately below the point at which the tube 4 enters the latter. Preferably the upper surface of this vane 53 is slightly concave and it may, if desired, be providedwith facentral aperture 54 sidewall of the tube 11 and is furnished with a crank ar'n '55 carrying an adjustable weight vane 53 is provided with a bracket 57 preferably. having an adjustable contact element 58, here shown as a set screw, which is adapted asthe vane swings downwardly to engage the head of the auxiliary valve device and to push the latter to the right as viewed in Fig. 2 in opposition to'the spring5O thus olosing the ports 42 in the cover 41 and simul When the valve is'thuspositionedthe chamber 29 of'the motor isfreely open tothe atmosphere and is entirely cut off from the '4 chamber 13'.-

In order to provide the' desired minimum flow, 1 herein employ a tube 59 leading from V the chamber 14 to the upper part'of the suction tube 7 controlling the passage of air through this tube means of a needle valve 60. While this means of providing theminimum flow is desirable, it is to be. understood that other and equivalent methods of providfollows Itbeing assumed that the parts desired. v The operation of the device 1s substantially ing for minimumflow maybe substituted if i normally occupy the position show-nlin Fig. 2, thatfa suitableflow pressure is maintained in the vacuum drum 8, and that the trans mission tube is empty. Under these circum- '6 and is passing-through thetransmission t5 ease and thence through the extension 4 When thefmain valve is. closed and the stances a small or minimum flow of air is constantly entering the open ended thermal The I .the chamber 29 of'the motor isopen .to the at? mosphere and is out otf from the transmis slon tube. The pressuresuponoppositesidesthe suction tube 7.

When *acarrier is introduced into the transmission tube, either at the open termi nal 6 or at the outlying station, this minimum flow is cut off or reduced in volume where- "thereof; the"chamber 13, and the tube 59, to a upon the increased suction in the chambers. 14and 13, acting through the open ports 42 inthe valve seat 41, produces av low pressure in the 'chamber' 49 of the motor and thus tends to raise the diaphragm 31 in opposition to the weight 34. The first effect of the upward, movement of the diaphragm 31 is to v v raise the pilot'member 22 ofthe controlling valve so as to uncover the apertures 19. Since these apertures are of relatively small area it is comparatively easy toliftthe pilot mem ber against the suction in thetube 7. so that the diaphragm responds sensitively to a very slight'redu'ction in'pressure. As soon as the pilot valve is open the pressures upon the up I per and lower sides'of the main member 1-7 ofsthe controlling valve become more nearly equal and. as the diaphragm continues to rise, the collar 24 engages the sleeve-2O and easily lifts the main member of the valve from its adjusted that the vane does not tilt to any "substantial extent under the action of the-carrier impelling air flow entering the chamberv 13-from the tube 4.' The parts as thus posi tioned are indicated in the Fig. 3.

When the carrier is delivered from the transmission tube there is a sudden'momentary increase "in velocity of .air th'roughthe transmission tube. This sudden rush of air issufficient to tilt the vane53 downwardly intothe position sh'own'in. Fig. 4, and since theabutment element 58 is normally spaced from the head 45, the vane 53 may acquire considerable momentum before the member 58 Y strikes'thehead 45 of the auxiliary valve. The vane may thus strike a blow of considerable force against the head 45 which "is suf-,

fi'io ficient toshift the auxiliary valve device into the position shown in:Fig. 4. In this position of the diaphragm 31 are thus almost-instantaneously equalizedand the weight 34 causes the controlling val-.ve ,to ';return to=- its "seat; very quickly.- The equalization of pressures upon opposite sides of .the' diaphragm and the closure of the controlling valve takes even though the vane 53 returns to its normal position immediately after its first contact with the valve head 45, the'controll-ing valve is closed with certainty at every downward movement ofthevane 53. l

rier-impelling flow cut ofi, the vane returns to its normal position if it has not already done so and tlie'spring 50 immediately restores auxiliary valve device to its normal po- 1 sition ready for a subsequent operation.

While the auxiliary valve arrangement herein disclosed is desirable for the purpose, I contemplate that other and equivalent arrangements might well be employed. For example, a rotary valve actuated directly or indirectly by the vane 53 might be substituted for the reciprocating valve herein disclosed, the essential being that in one position of the auxiliary valve device it shall cut oil atmospheric pressure from the motor chamberwhile ermitting the latter to communicate with the transmission tube, and in its other position that it shall cut off the motor chamber from the transmission tube and permit free communication between the motor chamher and the outer atmosphere.

I further contemplate that the vane 5-3 may be replaced equivalent devices, for examplc a reciprocatory battle plate or even by a pressure operated device responsive to the change in pressure conditions in the transmission tube incident to delivery of the carrier therefrom.

While 1 have herein described a controlling valve comprising a main portion and a pilot portion, and regard this as a desirable arrangement, it is to be understood that other types of valves may be substituted if desired since the particular form of valve employed does not constitute the main feature of the resent invention. It is also to be understood that the weight herein described as employed -for closing the controlling valve may be replaced by the usual spring and that the shape of the valve casing and associated parts may be varied as circumstances may indicate to be desirable.

lclaim:

1. Power control apparatus for a pneumatic dispatch system of the vacuum minimum flow type having a transmission tube and an ex-hauster connected to the tube, said apparatus comprising a controlling valve for governing carrier impelling airflow through the tube, a minimum flow or" air through the tube being permitted when the controlling valve is positioned to cut off carrier impelling flow, a pneumatic for moving the controllingvalve, auxiliary valve means adapted alter natively to open por s for admitting air at atmospheric pressure and at transmission tube pressure respectively to act on one side of the pneumatic, the auxiliary valve means being normally positioned to close one of saidports and to uncover the other, and means for shifting said auxiliary valve means when a carrier is delivered from the transmission tube whereby touncover the first port and to close the normally open port.

2. Power control apparatus for a pneu nease inaticdispatch system of the vacuum minimum flow type having a transmission tube and an exhauster connected to the tube, said apparatus comprising a controlling valve for governing carrier impelling air flow through the tube, a minimum flow of air through the tube being permitted when the controlling valve is positioned to cut off carrier impelling flow, apneumatic for moving the controlling valve, auxiliary valve means adapted alter natively to open ports of large capacity for admitting air at atmosphericpressure and at transmission tube pressure respectively to act on one side of the pneumatic, the auxiliary valve means being normally positioned'to close one o1 said ports and to uncover the other, and a device responsive to the rush of air through the transmission tube incident to governlng carrier impelling air flow throughthe tube, a minimum flow of air through the tube being permitted when the controlling valve is positioned to cut off carrier lmpelling flow, a pneumatic for opening the controlling valve to permit carrier impelling air flow through the tube, ports for admitting air at atmospheric pressure and at sub-atmospheric pressure respectively to act alternatively on one sid-eo'f the pneumatic, an auxiliary valve device normally occupying the same position when a carrier is in flight and when the tube is empty and when normally positioned closing one of said ports and leaving the other open, and an air actuated member responsive to conditions in the tube resulting from delivery of the last carrier therefrom for momentarily shifting said valve to uncover the nor mally closed port and to close the normally open port. V r V 4. Power control apparatus for a pneumatic dispatch system of the vacuum minimum flow type havinga' transmission tube and an exhauster connected to the tube, said apparatus comprising a controlling valve for governing carrier impelling air flow through the tube, a minimum flow of air through the tube being permitted when the controlling valve is positioned to cut off carrier impelling flow, a pneumatic for moving the controlling valve, ports for admitting air at atmospheric pressure and air substantially at suction tube pressure respectively to act alternatively on one side of the pneumatic, movable auxiliary valve means adapted to close each port, one port being closed when the other is open, and air operated means independent of i v n v V ments adapted toclosethe respectlve ports,

of said auxiliaryvalve means.

said pneumatic for determining the position apparatus comprising a controllingvalve for governing carrier impellingfair flow through i the-tube, a minimum flow ofairi through the tube being permitted when the controlling valve is positioned to out off carrier impelling floW, a casing, a pneumatic constituting a movable all for a chambervvithin' the easing,-said pneumatic being connected'to the controlling valveand adapted to'openthe latter to permit carrier impelling airfflow Ithroughthe tube, portswof large capacity providing communication between said chamber and theouter atmosphere and the transmission tube respectively, a valve hav ng ele- [said elementsbeingso arranged that when onecloses its port the other port is open, and

' 5 an air actuated devi'ce for moving said valve;

. 6'. Powerfcontrol apparatus fora pneumatlc dispatchsystenrof the vacuum ininl-i mum flow type having a 'transmissiontube and an exhauster connected'tothetube,'said apparatus comprising a controlling valvefor governing carrier impelling air flovvth'r ough the tube, a minimum flow-of a-ir'through the tube" being permitted1Whenthe eontrol'ling I I 'maticdispatch system of the vacuum minif valveis positioned to cutofij carrier impelling flow, a passage for admitting airto-actjupon one side of the pneumatic, said passage -hav- 111g dlvergent portlons'leadlng to the atmos-r phere and tojthe transmission tube respectively, auxiliary valve means normally closing one of said divergent portions of the passage-whileleaving the other open, and a member responsiveto the rushof air through the tube incident to 'thedischarge of a carrier from the latter and by its response shifting said valve means to open the firstfl divergent portlon of the passage. and to "close the other portion thereof. i

7. Power control for a pneumatio, dispatch system of the vacuum mini- I mum flow type having a transmission tube and an exha'uster connected to the tube, said I apparatus comprisinga controllingvalve for governing carrierimpellingair flow through the tube, a mln'imum flow of air through the tube beingfpermitte'd when the controlling valve is positioned to cut oft carrierimpel- 1mg flow, a pneumatlc responsive 'toireduc @1011 1n the mln mum flow incident to inser-r 'tion of a carrier the transmission tube,

.means connectlng the pneumatic to the controlling valve, one side of the pneumatic being normally exposed by means "of a normally open passage to a predetermined air pressure,

an auxiliary Valve element governing said passage, a movable actuator disposed in'the path of the air moving through the-tube and means normally retaining said movable actuator in inactive position, said actuator responding to the sudden rush of air through thetube incident to discharge of a carrier mum flow type havinga transmission tube and an exhauster connected to the tube, said apparatus comprising a controlling valve for governing carrier impelling air flow through thetube, a'minimum flow of air through the tube being permitted When the controlling valve is positioned .to cut off carrier impelling flow, an auxiliary valve device adapted alternatively to open ports for admitting air at atmospheric pressure and at transmission tube pressure respect vely to act on one 516.6

of the pneumatic, theauxiliary valve devicebeing normally positioned to close one of' movable vane for shifting said auxiliary valve device fronijnormal po'sltion to a poslsaid portsandto uncover the other; and a tion' in which the normally closed portcis .QJPVOWGI contro'l apparatusfor a pneumum flovv type having a transmission tube and an exhauster connected-to the tube,said

"apparatus comprising acontrolling valve for governing carrierimpelling air flow throughthe "tube, a minimum flow of air through the tube being permitted when the controlling valve is.-;posi tioned to cutoff carrier impelopen and the normally open port is-closed, said vane moving in respon'setoabnormal velocity of'air How in the transmission tube and thereby shifting the auxiliary valve delingffiovvQan auxiliary valve device adapted alternatively to open ports for admitting air I at atmospheric pressure and at transmission V tubepressure respectively to act on one side of the pneumatic, theauxiliaryvalve device being normally positioned-to close one of said; ports andto uncover the other, a tilting vane exposed to the current air 7 llowing through; the transmission tube, and yieldable means'for holding the vane in normal posis "if/i011, the van'etilting frorn normal position in'response to abnormalvelooity ofair flow and to close the normallyopen port.

matic dispatch system ofthe vacuum miniapparatus comprising a controlling valve for infthe tube and thereby shifting theauxiliary valve devi'ce to open the normally closed port j;

10. Povvercontrol apparatus for a pneugoverning carrier impelling air flovv through the tube, a minimum flow of air through the tube being permitted When the controlling valve is positioned to out OK carrier impel- ,ling fio'w, a casing, a'p'neumatic forming a movable wall member for a space Within the casing, said pneumatic being connected to the controlling valve and adapted to open the latter when the minimum flow is reduced by introduction of a carrier into the tube, a conduit leading to said chamber, said conduit having ports opening to the outer atmosphere and the interior of thetransmission tube respectively, a movable auxiliary valve stem, means tending to hold said stem in a predetermined normal position, spaced valve heads secured to the stem, said heads cooperating with the respective ports in the conduit, one head closing'its port when the other port is open, and an air operated device for moving the valve stem.

11. Power control apparatus for a pneumatic dispatch system of the vacuum minimum flow type having a transmission tube and an exhauster connected to the tube, said apparatus comprising a controlling valve for governing carrier impelling air flow through the tube, a minimum flow of air through the tube being permitted when the controlling valve is positioned to cut off carrier impelling flow, a casing, a pneumaticrforming a movable wall member for a space within the casing, said pneumatic being connected to the controlling valve and adapted to open the latter when the minimum flow is reduced by introduction of a carrier into the tube, a conduit leading to said chamber, said conduit having aligned ports opening respectively into the transmission tube and the outer atmosphere, an auxiliary valve stem extending from one port to the other, valve heads secured to the stem in spaced relation such that when one valvehead covers its port the other port is open, a spring tending to hold the stem in a predetermined normal position,

and an air actuated vane for moving the valve stem in opposition to the spring,

12'. Power control apparatus for a pneumatic dispatch system of the vacuum mini-.

mum flow type having a transmission tube and an exhauster connected to the tube, said apparatus comprising a controlling valve for governing carrier impelling air flow through the tube, a minimum fiow of air through the tube being permitted when the controlling valve is positioned to cut oil carrier impelling flow, a pneumatic response to reduction in the minimum flow incident to insertion of a carrier in the transmission tube, means connecting the pneumatic to the controlling valve, one side of the pneumatic being normally exposed by means of a normally open passage to transmission tube pressure, and means independent of the pneumatic for closing said passage and permitting the entrance of air at atmospheric pressure to act on said side of the pneumatic.

13. Power control apparatus for a pneumatic dispatch system of the vacuum mini mum flow type having a transmission tu e and an exhauster connected to the tube, said apparatus comprising a controlllng valve for governing carrier impelling air flow through the tube, a minimum flow of air through the .valve to close said passage.

14. Power controlled apparatus for a pneumaticdispatch system of the vacuum minimum flow type having a transmission tube and an exhauster connected to the tube, said apparatus comprising a controlling valve for governing carrier impelling air flow through the tube, a minimum'fiow of airthroughtha tube being permitted when the controlling-b valve is positioned to cut ofi carrier impelling flow, a pneumatic responsive to reduction 1n .7 the minimum flow incident to insertion of a carrier inthe transmission tube, means connecting the pneumatic to the controlling '95 valve, oneside of the pneumatic being normallyexposed' by means of a normally open passage to transmission tube pressure, an auxiliary valve element'for governing said normally open passage, means tending to retain'uoo said auxiliary valve in inoperative position, and means responsive to the delivery ofa carrier from the tube for imparting a sudden blow to the auxiliary valve to cause it to close said passage.

15. Power control apparatus for a pneumatic dispatchsystemof the vacuum minimum flow type having a transmission tube and an exhauster connected to the tube, saidapparatus comprising a controlling valve for governing carrier impelling air flow through the tube, a minimum flow of air through the tube being permitted when the controlling valve is positioned to cut off carrier impelling flow, a pneumatic responsive to reduction in 1 the minimum flow incident to insertion 01" a carrier in the transmissiontube, means connecting the pneumatic to the controlling valve, one side of the pneumaticbeing nor- ,mally exposed by means of a normally open mum flowtype having atransmission tube and an exhanster connected to the tube, said appav ratus comprising a controlling valve for governmg carrier impelling air flow through the tube, a minimum flow of air'thro'ugh the tube being permitted when the controlling valve is positioned to cut oil carrierimpelling flow,

' a pneumatic responsive to reduction in the to transmission tube pressure, an auxiliary valve element governing 'said'passage, a .pivotedvane disposed in the path of a1r flowing through the tube,an abutment carried by the vane adapted'to engage the auxiliaryvalve and to move the latterto passage closing position, and means normally holding the vane in inactive position with its abutment spaced from the auxiliary valve.

17. Power control apparatus for a pneu matic dispatch system of the vacuum minimum flow type having a transmissiontube and an exhauster connected to the tube, said apparatus comprising a controlling valve for g'ove erning carrier impelling air flow through the tube, a minimum flow of air through the tube being permitted when the controlling valve is positioned to cut off carrier impelling flow, a pneumatic responsive to reduction in the minimum flow incident to insertion of a carrier in the transmission tube, means connecting the pneumatic to the controlling valve, one side of the pneumatic being normally exposed by means of a normally open passage to transmission tube pressure, an auxiliary valve for vclosing said normally open passage, "and an air actuated vane responsive to-"the rush of a carrier therefrom for moving said auxiliary valve. I

18. Power control apparatus for a pneumatic dispatch system of the vacuum minimum flow type having a transmission tube andan' exhauster connected to the tube, said apparatus comprising a controlling valve for governing carrier impelling air fiow'through' the tube, a minimum flow of air through the tube being permitted when the controlling the tube for shifting said auxiliary valveelements to close said passage. and to open said port. V

19. Power control apparatus for a pneumatic dispatch system of the vacuum minimum flow type having a transmission tube and an exhauster connected to the tube, said apparatus comprising a cont-rolling valve for governing carrier impelling air flow through the tube, a minimum flow of air through the tube being permitted when the controlling valve is positioned to cut off carrier impelling so e pneumatic responsive to reduction 1n the'minimum flow incident to insertion of a carrier in the transmissiontube, means connecting the pneumatic to' the controlling valve, one side of the pneumatic being normally exposed by means of a normally open passage to transmission tube pressure, an auxilia ry'valveelement for'closing said norof the pneumatic, and a vane'responsiveto the sudden rush of air throughthe tube incident to delivery of a carrierfr'om the tube for moving s'aidauxiliary valve elements to close said passage and to open said port.

Signed by me at Syracuse, New York, this 14th day of January, 1926. l

, CHESTER S. JENNINGS.

, 7 I 105 7 air through the tube incident to discharge of l valve is positioned to cut off carrier impel-' ling flow, a pneumatic responslve to reduction in the minimumfiow incident to insertion of a carrier in the transmission tube, means con necting the pneumatic to the controlling valve, one side of the pneumatic being nor- 7 anally exposed by means of a normally open passage to transmission tube pressure, an auxiliary valve element for closing saidnormally open passage, a second auxiliary valve element normally closing a port for admitting air at atmospheric pressure to act on said side of the pneumatic,fand a device respon sive. to variation in the rate, of flow of air in I p mally open passage, a second auxiliary valve, V 1 element normally closinga port for admitting air at atmospheric pressurefto act onsaid side 

